anaesthetics Flashcards
1
Q
what category of medicine is a topical anaesthetic
A
POM (prescription only medicine)
so only healthcare professionals have access to them
2
Q
topical anaesthetics are drugs that ____________ block ________________ in ____________ nerves
A
topical anaesthetics are drugs that reversibly block transmission in sensory nerves
3
Q
list 5 indications for use of a topical anaesthetic
A
- contact tonometry
- contact lens fitting
- foreign body removal
- gonioscopy
- lacrimal procedures
4
Q
what indication will you never use a topical anaesthetic for
A
the relief of symptoms
5
Q
what type of contact lens fitting will you use a topical anaesthetic
A
if your going to make an impression of the eye e.g. for scleral lenses
6
Q
what does topical anaesthetics delay
A
corneal epithelial cell healing, so it is not good for a patient with corneal abrasions
7
Q
list 3 advantages of topical anaesthetics
A
- allows certain procedures to be conducted
- makes the patient more comfortable
- makes procedures easier for the practitioner
8
Q
list 4 disadvantages of topical anaesthetics
A
- stings (due to pH)
- delays healing
- eye is more susceptible to damage (due to delayed healing, it is more compromised)
- repeated installations
9
Q
the most mode action of topical anaesthetic
- _________ information passes along _______ _______ __________ _________ (action potentials)
- nerve has __________ charge at _______
- _______ ________ is generated in _______ of _________ ions into the ________ and this results in a _________ charge (depolarisation)
- efflux of __________ ions returns the nerve to _________ potential causing _______________
- the action potential passes along the nerve along with _____________ ___________ and depolarisations of ________ areas
- topical anaesthetics __________ block nerve conduction
- they block ___________ channels therefore action potentials ______ be generated
A
- sensory information passes along nerve fibres electrical impulses (action potentials)
- nerve has negative charge at rest
- action potential is generated in influx of sodium ions into the nerve and this results in a positive charge (depolarisation)
- efflux of potassium ions returns the nerve to resting potential causing repolarisation
- the action potential passes along the nerve along with successive depolarisations and depolarisations of adjacent areas
- topical anaesthetics reversibly block nerve conduction
- they block sodium channels therefore action potential can’t be generated
10
Q
which topical anaesthetic stings the most
A
amethocaine (tetracaine)
11
Q
what is the onset and duration of amethocaine
A
onset 1 min
duration 20 min
12
Q
what is the onset and duration of benoxinate
A
onset 1 minute
duration 15 minutes
13
Q
what is the onset and duration of proxymetacaine
A
onset 1 minute
duration 15 minutes
14
Q
what is the onset and duration of lignocaine
A
onset 1 minute
duration 30 minutes
15
Q
what is another name for amethocaine
A
tetracaine
16
Q
what is another name for benoxinate
A
oxybuprocaine
17
Q
what is another name for proxymetacaine
A
proparacaine
18
Q
what is another name for lignocaine
A
lidocaine
19
Q
which topical anaesthetic has the longest duration
A
lignocaine
20
Q
what are the 2 types of possible chemical structures of topical anaesthetics
A
- ester link
or - amide link
21
Q
which chemical structure of topical anaesthetic is more linked to allergic reactions
A
ester link
22
Q
what is the ester link chemical structure hydrolysed by
A
cholinesterase
23
Q
what is the amide link resistant to
A
hydrolysation
24
Q
which chemical structure has a longer duration
A
amide link
25
list the 3 ester link topical anaesthetics
- oxybuprocaine
- tatracaine
- proparacaine
26
what is the amide link topical anaesthetic
lignocaine
27
what portions/parts do all of the topical anaesthetics have
lipophilic (insoluble) and hydrophilic (soluble) parts that are linked together either by an ester link or an amide link
28
which chemical strict of topical anaesthetic is broken down more easily
ester linkage
29
which topical anaesthetic is the most potent and provides the deepest anaesthesia and what does this make it good for
tertacaine (amethocaine)
makes it good for foreign body removal
30
sensitivity of tetracaine/amethocaine is _________ and occurs after ____________ _________
sensitivity of tetracaine/amethocaine is rare and occurs after repeated doses
31
what is tetracaine/amethocaine associated with
punctate staining
32
list the 4 contraindications/cautions of tetracaine/amethocaine
- sulphonamides
- premature babies
- known allergy
- pregnancy/lactation
33
what form of packaging and what doses is tetracaine/amehocaine available in and what are the storage conditions
- 0.5% and 1.0%
- minims
- protect from light (a cupboard stops it from destabilising)
34
what may happen if tetracaine/amethocaine is not protected from light
it will be hydrolysed by the light, causing it to destabilise
35
how can tetracaine/amethocaine damage the cornea
if the solution dose is over 1% concentration
36
what is it possible to do after just one drop of tetracaine/amethocaine
removal or foreign body
37
which topical anaesthetic is the most widely used by optometrists in the UK
oxybuprocaine/benoxinate
38
how likely are sensitivity reactions with oxybuprocaine/benoxinate
rare
39
what does oxybuprocaine/benoxinate have less of that tetracaine/amethocaine
less stinging, irritation
40
what special property does oxybuprocaine/benoxinate have and how can this also be a disadvantage
bactericidal properties
but when want to take a swab of the eye to test for bacteria it produces false results as it has killed some of it off
41
list the 4 contraindications/cautions of oxybuprocaine/benoxinate
- known allergy
- if other eyedrops containing chlorhexidine acetate as a preservative are being used
- pregnancy/lactation
- premature babies
42
what form of packaging and dose is oxybuprocaine/benoxinate available in and what is the storage conditions
- 0.4%
- minims
- store below 25 degrees celsius and protect from light
43
how can oxybuprocaine/benoxinate be used in ophthalmology
- three drops are instilled over a five minute interval which allows foreign body to be removed
- corneal sensation recovers after one hour
44
which topical anaesthetic stings the least
proxymetacaine/proparacaine
45
proxymetacaine/proparacaine causes the minimal __________ ___________ __________, ideal for ___________
proxymetacaine/proparacaine causes the minimal punctate corneal staining, ideal for tonometry
46
why is proxymetacaine/proparacaine used in hospitals more and what is it useful for
because it has the least antibacterial properties, useful when taking conjunctival swabs
47
list the 5 contraindications/cautions with proxymetacaine/proparacaine
- known allergy
- overactive thyroid
- heart disease
- premature babies
- pregnancy/lactation
48
how common is sensitivity with proxymetacaine/proparacaine
rare
49
what form of packaging and dose is proxymetacaine/proparacaine available in and what are the storage conditions
- 0.5%
- minims
- store between 2-8 degrees celsius - has to be kept in a refrigerator
50
what type of surgery can proxymetacaine/proparacaine be used in and how is it used in this condition
cataract extraction
1 drop every 5 - 10 minutes
5 - 7 drops in total
51
which other topical anaesthetic does lidocaine/lignocaine sting less that
tetracaine/amethocaine
52
when is lidocaine/lignocaine used
when a patient is sensitive to the ester link
53
what are the contraindications/cautions with lidocaine/lignocaine
- pregnancy/lactation
| - premature babies
54
why is lidocaine/lignocaine good for goldmann tonometry
because it comes combined with fluorescein
55
what form of packaging and dose does lidocaine/lignocaine come in and what are the storage conditions
- 4% minims combined with 0.25% flourescein
- minims
- store below 25 degrees celsius and protect from light
56
what dosage of fluorescein does lidocaine/lignocaine come with
0.25%
57
list 6 possible side effects that can occur with any topical anaesthetic from least to most worse
- transient stinging
- transient blurring
- conjunctival hyperaemia
- mild superficial epithelial damage, especially with stronger drops such as tetracaine which represents local toxicity
- punctate keratitis
- hypersensitivity reactions (less likely with lidocaine), range from mild transient blepharoconjunctivitis to diffuse necrotising epithelial keratitis
58
what is the incidence of necrotising keratitis incidence with ester drugs
1/1000
59
repeated use can lead to __________ ____________ can lead to _______________ _______________
repeated use can lead to epithelial toxicity can lead to serious keratopathy
60
what 4 things can serious keratopathy lead to
- epithelial loss
- stromal oedema
- corneal infiltrates
- anterior chamber reaction
61
what must you instruct to your patient in regards to topical anaesthetics
not to rub the eyes
| cannot leave practice until anaesthetic had worn off
62
what is increased by instillation of topical anaesthetic
permeability of epithelium cells thus enhances effect of other drugs e.g. when using in combination with cyclopentolate in dark eyes
63
what is reduced by topical anaesthetics
healing of epithelial cells
64
who is topical anaesthetics open to abuse by
health care practitioners
